This invention relates to a method of shaping coils and has particular application in the shaping of coils comprising helically wound bare wires for use in a radiant heater of a smooth top cooker in which there is little or no other constraint on the winds of the coil.
A "smooth top" cooker is one in which a smooth top, normally of glass ceramic, overlays one or more generally circular electric heater elements supported on a layer of thermal and electrical insulating material such that the element is spaced from the top. In use, a utensil placed on the top over an element is heated by the transmission of heat from an element to and through the top by air convection, conduction and infra red radiation. Such elements are referred to as "radiant heaters". The insulating material substantially prevents heat being transmitted away from the element except towards the top and as the preferred materials for the top are essentially thermally non-conductive, only areas of the top which are "exposed" to the element will be heated. In order to prevent heat being transmitted to parts of the top not covered by a utensil placed thereon, a peripheral wall of insulating material is also normally provided around the element.
In radiant heaters of the above kind, the coil used is typically an iron chromium aluminium resistance heating wire and is very springy in nature. Reference is directed to our copending application Ser. No. 118,951 which is directed to a development in radiant heaters of this type. The complex shapes now used in radiant heaters require the heating coil to be very firmly secured to its support. This can be time consuming and expensive, and can also damage the insulating material of the support. The present invention is a method by which the securement of a coil to its support in a radiant heater is facilitated.